Solar module

ABSTRACT

A solar module is provided which has improved durability. A third wiring member ( 32   a ) includes a first portion ( 32   a   1 ), a second portion ( 32   a   2 ), and a third portion ( 32 a 3 ). In the first portion ( 32   a   1 ), metal foil ( 52 ) faces a solar cell ( 20 ). The first portion ( 32 a 1 ) is electrically connected to the solar cell ( 20 ). The second portion ( 32   a   2 ) is arranged on the solar cell ( 20 ) with the metal foil ( 52 ) facing the side opposite to the solar cell ( 20 ). The third portion ( 32   a   3 ) connects the first portion ( 32   a   1 ) and the second portion ( 32   a   2 ). A first wiring member ( 32   b ) electrically connects the second portions ( 32   a   2 ) of adjacent solar cell strings ( 10 ) to each other. The solar module ( 1 ) also includes an insulating sheet ( 60 ). The insulating sheet ( 60 ) is arranged between the first wiring member ( 32   b ) and the solar cell ( 20 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of International Application PCT/JP2012/063502,with an international filing date of May 25, 2012, filed by applicant,the disclosure of which is hereby incorporated by reference in itsentirety.

FIELD OF THE INVENTION

The present invention relates to a solar module.

BACKGROUND

Solar modules with back contact solar cells are conventionally known tobe solar modules with improved photoelectric conversion efficiency. Anexample is described in Patent Document 1. The solar module described inPatent Document 1 includes a plurality of circuit boards with wiringprovided on the surface. The back contact solar cells are arranged inone direction on the circuit boards. The solar cells are connectedelectrically to the wiring of the circuit boards. The circuit boards arearranged in another direction which is perpendicular to the onedirection. Circuit boards adjacent to each other in the other directionare connected electrically via conductive members.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Laid-Open Patent Publication No. 2009-43842

SUMMARY Problem Solved by the Invention

In recent years, there has been growing demand for solar modules withimproved durability.

It is an object of the present invention to provide a solar module withimproved durability.

Means of Solving the Problem

The solar module of the present invention includes a plurality of solarcell strings and a first wiring member. The solar cell strings arearranged in the one direction. The first wiring member is used toelectrically connect adjacent solar cell strings to each other. Thefirst wiring member is composed of metal foil. Each solar cell stringhas a plurality of solar cells, a second wiring member, and a thirdwiring member. The solar cells are arranged in another directioninclined with respect to the one direction. The second wiring member isbonded to the end portions of each of the adjacent solar cells. Thesecond wiring member is used to connect adjacent solar cells to eachother. The third wiring member is electrically connected to the endportion in the other direction of the solar cell positioned at the veryend of the solar cells in the other direction. The third wiring memberhas resin film and metal foil arranged on the resin film.

The third wiring member includes a first portion, a second portion, anda third portion. In the first portion, the metal foil faces the solarcell. The first portion is connected electrically to the solar cell. Thesecond portion is provided on the solar cell with the metal foil facingthe side opposite to the solar cell. The third portion connects thefirst portion and the second portion. The first wiring member is used toelectrically connect the second portions of adjacent solar cell stringsto each other. The solar module of the present invention also includesan insulating sheet. The insulating sheet is arranged between the firstwiring member and the solar cell.

Effect of the Invention

The present invention is able to provide a solar module with improveddurability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified back view of a solar module in an embodiment ofthe present invention.

FIG. 2 is a simplified cross-sectional view from line II-II in FIG. 1.

FIG. 3 is a simplified back view of a solar module in an embodiment ofthe present invention.

FIG. 4 is a simplified cross-sectional view of the solar cell string insection IV of FIG. 2.

FIG. 5 is a simplified cross-sectional view of the solar cell string insection V of FIG. 2.

FIG. 6 is a simplified back view of the solar module in a modifiedexample.

DETAILED DESCRIPTION

The following is an explanation of examples of preferred embodiments ofthe present invention. The following embodiments are merely examples.The present invention is not limited by the following embodiments in anyway.

Further, in each of the drawings referenced in the embodiments, membershaving substantially the same function are denoted by the same symbols.The drawings referenced in the embodiments are also depictedschematically. The dimensional ratios of the objects depicted in thedrawings may differ from those of the actual objects. The dimensionalratios of objects may also vary between drawings. The specificdimensional ratios of the objects should be determined with reference tothe following explanation.

As shown in FIG. 1 and FIG. 2, the solar module 1 is provided with aplurality of solar cell strings 10 each having a plurality of solarcells 20. More specifically, the solar module 1 includes a first throughsixth solar cell string 10 a-10 f. As shown in FIG. 2, the solar cellstrings 10 are arranged between a first protecting member 11 and asecond protecting member 12. The first protecting member 11 ispositioned on the side with the light-receiving surfaces 20 a of thesolar cells 20. The second protecting member 12 is positioned on theside with the back surfaces 20 b of the solar cells 20. The secondprotecting member 12 is flexible. A sealing material layer 13 isprovided between the first protecting member 11 and the secondprotecting member 12. The solar cells 20 are sealed by the sealingmaterial layer 13.

The first protecting member 11 can be composed of a translucent membersuch as a resin substrate. The second protecting member 12 can becomposed of a flexible member such as a resin sheet or a resin sheetcontaining interposed metal foil. The sealing material layer 13 can becomposed of ethylene-vinyl acetate copolymer (EVA), polyvinyl butyral(PVB), polyethylene (PE), or polyurethane (PU). The sealing materiallayer 13 preferably contains a non-crosslinked resin.

Each of the solar cell strings 10 has a plurality of solar cells 20arranged in the x-axis direction, which is inclined with respect to(usually perpendicular to) the y-axis direction or the direction inwhich the solar cell strings 10 are arranged. As shown in FIG. 1 andFIG. 3, each solar cell 20 has a photoelectric conversion unit 23, andfirst and second electrodes 21, 22.

The photoelectric conversion unit 23 has first and second main surfaces23 a, 23 b. The first main surface 23 a of the photoelectric conversionunit 23 constitutes the light-receiving surface 20 a of the solar cell20, and the second main surface 23 b constitutes the back surface 20 bof the solar cell 20.

A photoelectric conversion unit 23 is a member that generates carrierssuch as holes and electrons when exposed to light. The photoelectricconversion unit 23 may generate carriers when exposed to light only onthe first main surface 23 a, or may generate carriers when exposed tolight not only on the first main surface 23 a but also on the secondmain surface 23 b. In other words, the solar cells 20 may be bifacialsolar cells.

There are no particular restrictions on the type of photoelectricconversion unit 23 that is used. The photoelectric conversion unit 23can, for example, be composed using a crystalline silicon substrate.

A first electrode 21 for collecting one of either electrons or holes anda second electrode 22 for collecting the other of either electrons orholes are arranged on the second main surface 23 b of the photoelectricconversion unit 23. In other words, the solar cells 20 are back contactsolar cells.

There are no particular restrictions on the shape of either the firstelectrode 21 or the second electrode 22. In the present invention, boththe first electrode 21 and the second electrode 22 are comb-shaped. Thefirst electrode 21 and the second electrode 22 are interdigitated. Morespecifically, the first electrode 21 and the second electrode 22 bothhave a plurality of finger portions 21 a, 22 a and a busbar portion 21b, 22 b. Each of the finger portions 21 a, 22 a extends in the x-axisdirection. Finger portions 21 a, 22 a are arranged at a predeterminedinterval in the y-axis direction, which is perpendicular to the x-axisdirection.

The finger portions 21 a are connected electrically to busbar portion 21b. Busbar portion 21 b is arranged on one side (the x1 side) of thefinger portions 21 a in the x-axis direction. Busbar portion 21 b isprovided from one end to the other in the y-axis direction on the x1 endportion of the solar cell 20 in the x-axis direction.

Similarly, the finger portions 22 a are connected electrically to busbarportion 22 b. Busbar portion 22 b is arranged on one side (the x2 side)of the finger portions 22 a in the x-axis direction. Busbar portion 22 bis provided from one end to the other in the y-axis direction on the x2end portion of the solar cell 20 in the x-axis direction.

As shown in FIG. 1, adjacent solar cells 20 in the x-axis direction areconnected electrically using a wiring member 31 in each of the solarcell strings 10. More specifically, the first electrode 21 of one of thesolar cells 20 adjacent to each other in the x-axis direction isconnected electrically by a wiring member 31 to the second electrode 22of the other solar cell 20.

The wiring member 31 can be composed of metal foil, a metal foillaminate, metal foil whose surface is coated with solder, or a flexibleprinted circuit (FPC) board having an insulating film and wiringarranged on the insulating film. The metal foil and the wiring can bemade of Ag or Cu.

The wiring member 31 and the back surface 20 b of a solar cell 20 arebonded via an adhesive layer (not shown). The adhesive layer can becomposed of a cured resin adhesive, a cured resin adhesive containing adispersed conductive material, or solder. The wiring member 31 is bondedto the end portion of the solar cell 20 in an x-axis direction. Morespecifically, the wiring member 31 is bonded only to the end portion ofthe solar cell 20 in an x-axis direction.

The first through sixth solar cell strings 10 a-10 f are connectedelectrically via a wiring member 32. More specifically, the solar cell20A at the farthest x2 end of the first solar cell string 10 a, thesolar cell 20B at the farthest x2 end of the second solar cell string 10b, the solar cell 20C at the farthest x2 end of the third solar cellstring 10 c, the solar cell 20D at the farthest x2 end of the fourthsolar cell string 10 d, the solar cell 20E at the farthest x2 end of thefifth solar cell string 10 e, and the solar cell 20F at the farthest x2end of the sixth solar cell string 10 f are each connected electricallyby a wiring member 32. The wiring member 32 electrically connects thefirst electrodes 21 of solar cells 20A, 20C and 20E to the secondelectrodes 22 of solar cells 20B, 20D and 20F.

In addition, the solar cell 20H at the farthest x1 end of the secondsolar cell string 10 b, the solar cell 20I at the farthest x1 end of thethird solar cell string 10 c, the solar cell 20J at the farthest x1 endof the fourth solar cell string 10 d, and the solar cell 20K at thefarthest x1 end of the fifth solar cell string 10 e are connectedelectrically by a wiring member 32. The wiring member 32 electricallyconnects the first electrode 21 of solar cells 20H and 20J to the secondelectrode 22 of solar cells 20I and 20K.

A portion of wiring member 32 electrically connecting solar cells 20Hand 20I, and a portion of wiring member 32 electrically connecting solarcells 20J and 20K create a first extraction electrode 41. As shown inFIG. 2, the first extraction electrode 41 is drawn from the sealingmaterial layer 13 and, more specifically, the solar module 1. Morespecifically, the tip of the first extraction electrode 41 is drawn fromthe second protecting member 12.

The wiring member 32 is actually composed of two wiring members 32 a andwiring member 32 b. The two wiring members 32 a are bonded via anadhesive layer 40 to the solar cell 20, and are connected electricallyto the first electrode 21 or the second electrode 22. Wiring member 32 bis connected electrically to the two wiring members 32 a. Wiring member32 a is arranged in the y-axis direction perpendicular to the x-axisdirection from the y1 end to the y2 end of the end portion of the solarcell 20 in the x-axis direction. The wiring member 32 a is connectedelectrically to the solar cell at the far end in the x-axis direction ofthe solar cells 20 constituting a solar cell string 10.

As shown in FIG. 4, the wiring member 32 a is composed of a flexibleprinted circuit board having a resin film 51 and wiring 52. The resinfilm 51 can be made of a resin such as polyimide (PI) or polyethyleneterephthalate (PET). The wiring 52 is arranged on the resin film 51. Thewiring 52 is connected electrically to the first electrode 21 or thesecond electrode 22. The wiring 52 can be composed of metal foil made ofat least one type of metal such as Cu or Ag.

The wiring member 32 a has a first portion 32 a 1, a second portion 32 a2 and a bent portion 32 a 3. The first portion 32 a 1 constitutes oneend of the wiring member 32 a. The first portion 32 a 1 is arranged sothat the wiring 52 faces the solar cell 20. The first portion 32 a 1 isbonded to the back surface 20 b of the solar cell 20.

The second portion 32 a 2 constitutes the other end of the wiring member32 a. The second portion 32 a 2 is arranged so that the wiring 52 facesthe side opposite to the solar cell 20. At least a section of the secondportion 32 a 2 is arranged on the first portion 32 a 1. In other words,at least a section of the second portion 32 a 2 overlaps with the firstportion 32 a 1 in the z-axis direction, which is the thickness directionof the solar cell 20.

The bent portion 32 a 3 is connected to the first portion 32 a 1 and thesecond portion 32 a 2. The bent portion 32 a 3 has a bent structure. Inthe bent portion 32 a 3, the wiring 52 faces outside. The bent portion32 a 3 is arranged on the back surface 20 b of the solar cell 20. Inother words, the bent portion 32 a 3 overlaps with the solar cell 20 inthe z-axis direction. The bent portion 32 a 3 is formed by bending aflat wiring member.

Wiring member 32 b is connected electrically to the wiring 52 of thewiring member 32 a in the second portion 32 a 2. In other words, thewiring member 32 b connects the second portions 32 a 2 of solar cellstrings 10 adjacent to each other in the y-axis direction. The wiringmember 32 b is arranged so as to overlap with the second portion 32 a 2in the x-axis direction. The wiring member 32 b may be bonded to thewiring member 32 a using a resin adhesive. In the present invention, itis bonded to the wiring member 32 a using solder and is connectedelectrically to the wiring 52 of the wiring member 32 a. The wiringmember 32 b is bonded to a portion of the wiring member 32 a in they-axis direction. The ratio of the length of the portion of wiringmember 32 a bonded to wiring member 32 b in the y-axis directionrelative to the length of wiring member 32 a in the y-axis direction((length of wiring member 32 a bonded to wiring member 32 b in they-axis direction)/(length of wiring member 32 a in y-axis direction)) ispreferably from 1/10 to 1, and more preferably from 1/10 to ½.

A portion of wiring member 32 b constitutes extraction electrode 41 andis drawn from the solar module 1.

In the present invention, the wiring member 32 b is composed of metalfoil of at least one type of metal such as Cu or Ag. The thickness ofthe wiring member 32 b is greater than the thickness of the wiring 52.The thickness of the wiring member 32 b is two or more times greater,and preferably 5 or more times greater, than the thickness of the wiring52.

The second electrode 22 of the solar cell 20G at the farthest x1 end ofthe first solar cell string 10 a and the first electrode 21 of the solarcell 20L at the farthest x1 end of the sixth solar cell string 10 f areconnected electrically by wiring member 33. Solar cells 20G and 20L arebonded to the wiring member 33 via an adhesive layer 40.

Wiring member 33 has wiring member 32 a and wiring member 33 b. Thewiring member 32 a constituting a portion of wiring member 33 has aconfiguration that is substantially similar to the wiring member 32 aconstituting a portion of wiring member 32. Wiring member 32 aconstituting a portion of wiring member 33 is bonded and connectedelectrically to the second electrode 22 of solar cell 20G and the firstelectrode 21 of solar cell 20L.

Wiring member 33 b is connected electrically to wiring member 32 aconstituting a portion of wiring member 33. A portion of wiring member33 b constitutes extraction electrode 42. The extraction electrode 42 isdrawn from the sealing material layer 13, more specifically, from thesolar module 1.

The wiring member 33 b is connected electrically to the wiring 52 in thesecond portion 32 a 2 of the wiring member 32 a constituting a portionof wiring member 33. The wiring member 33 b may be bonded to the wiringmember 32 a using a resin adhesive. However, in the present embodiment,it is bonded to the wiring member 32 a using solder and connectedelectrically to the wiring 52 of the wiring member 32 a. The wiringmember 33 b is bonded to a portion of the wiring member 32 a in they-axis direction.

In the present embodiment, the wiring member 33 b is composed of metalfoil made of at least one type of metal such as Cu and Ag. The thicknessof the wiring member 33 b is greater than the thickness of the wiring52. The thickness of the wiring member 33 b is 2 or more times greater,and preferably 5 or more times greater, than the thickness of the wiring52.

An insulating sheet 60 is arranged between the back surface 20 b of thesolar cell 20 and the wiring members 32 b, 33 b and extractionelectrodes 41, 42 made of metal foil. This can prevent shorting of thewiring members 32 b, 33 b, the extraction electrodes 41, 42 and theelectrodes 21, 22. The insulating sheet 60 can be made of the PI or PETresin used in the resin film 51 or can be made of EVA, PVB, PE or PUresin used in the sealing material layer 13. The insulating sheetarranged between the wiring members 32 b, 33 b and the solar cell 20 canbe separate from the insulating sheet arranged between the extractionelectrodes 41, 42 and the solar cell 20.

Here, the thermal expansion coefficient of the printed circuit board isdifferent from the thermal expansion coefficient of the solar cell. Asin the solar module described in Patent Document 1, this makes it sothat a circuit board and a solar cell easily delaminate when the entiresurface of a back contact solar cell is bonded to a circuit board.

In the solar module 1, the wiring member 31 is not bonded to the entiresurface of a solar cell 20 but only to the end portion of the solar cell20 in the x-axis direction. In this way, it is difficult for a largeamount of stress to occur between the wiring member 31 and the solarcell 20 when the temperature of the solar module 1 changes. This makesdelamination of the wiring member 31 and the solar cell 20 less likelyto occur.

Similarly, the wiring member 32 a is connected electrically to a solarcell 20 at the end portion of the solar cell 20 in the x-axis direction.The second portions 32 a 2 of wiring members 32 a in solar cell strings10 arranged adjacent to each other in the y-axis direction are connectedto each other electrically via a wiring member 32 b of metal foil. Aninsulating sheet 60 is arranged between the wiring member 32 b and thesolar cells 20. The insulating sheet 60 insulates the wiring member 32 band the solar cells 20. When this configuration is used, it is difficultfor a large amount of stress to occur between the wiring member 32 b andthe solar cells 20 when the temperature of the solar module 1 changes.This makes delamination of the wiring member 32 b and the solar cell 20less likely to occur. As a result, a solar module 1 with improveddurability can be realized.

In a configuration in which two wiring members 32 a are connected via awiring member 32 b, a portion of a wiring member 32 b may come intocontact with the first electrode 21 or the second electrode 22 of thesolar cell 20. In order to prevent current leakage due to contact, aninsulating sheet may be provided between the wiring member 32 b and thesolar cell 20.

However, when an insulating sheet is provided in this portion, a leveldifference occurs between the region in which wiring member 32 a isprovided and the region in which wiring member 32 b is provided, and thewiring member 32 b connected to wiring member 32 a may come off. This islikely to occur when the solar cells 20 are sealed inside the sealingmaterial layer 13.

In the present embodiment, an insulating sheet 60 is provided not onlyin the region in which wiring member 32 b is provided but also in theregion in which wiring member 32 a is provided. As a result, theconnection reliability between wiring member 32 a and wiring member 32 bcan be improved while insulating wiring member 32 b and the solar cell20.

When this configuration is used, the size of the insulating sheet 60 canbe reduced. In this solar module 1, the wiring member 32 b is providedso as to overlap with the second portion 32 a 2 in the x-axis direction.As a result, the length of the region in which the second portion 32 a 2and the wiring member 32 b are provided can be reduced in the x-axisdirection. This further reduces the size of the insulating sheet 60. Themanufacturing costs of the solar module 1 can be lowered by reducing thesize of expensive insulating sheets 60.

In solar module 1, the length of the second portions 32 a 2 in thex-axis direction of solar cell strings 10 a and 10 f positioned to theoutside in the y-axis direction is the same as the length of the secondportions 32 a 2 in the x-axis direction of solar cell strings 10 b-10 epositioned in the center in the y-axis direction. However, as shown inFIG. 6, the solar cell strings 10 of solar module 2 include solar cellstrings 10 whose second portions 32 a 2 have different lengths in thex-axis direction. More specifically, the length of the second portions32 a 2 in the x-axis direction of solar cell strings 10 a and 10 fpositioned to the outside in the y-axis direction is different from thelength of the second portions 32 a 2 in the x-axis direction of solarcell strings 10 b-10 e positioned in the center in the y-axis direction.The extraction electrode 42 is connected electrically to the longersecond portions 32 a 2 of solar cell strings 10 b-10 e in a portioncloser to the center of the solar cell module 2 than the shorter secondportions 32 a 2 of the solar cell strings 10 a, 10 f. The portion of theextraction electrode 42 on the side with the second portion 32 a 2extends away from the second portion 32 a 2 in the y-axis direction.Unlike solar module 1, solar module 2 does not require a bent portion inthe portion of the extraction electrode 42 on the side with the secondportion 32 a 2. This reduces manufacturing costs associated with theextraction electrode 42. As a result, the manufacturing costs of thesolar module 2 can be reduced.

The present invention includes various embodiments not described herein.For example, the first and second electrodes may be busbarlesselectrodes which have finger portions but no busbar portion.

A solar module may also include a single solar cell.

The present invention includes many other embodiments not describedherein. Therefore, the technical scope of the present invention isdefined solely by the items of the invention specified in the claimspertinent to the above explanation.

KEY TO THE DRAWINGS

-   1: Solar module-   10, 10 a-10 f: Solar cell strings-   11: 1st protecting member-   12: 2nd protecting member-   13: Sealing material layer-   20, 20A-20L: Solar cells-   20 a: Light-receiving surface-   20 b: Back surface-   21: 1st electrode-   22: 2nd electrode-   23: Photoelectric conversion unit-   31-33, 32 a, 32 b, 33 b: Wiring members-   32 a 1: 1st portion-   32 a 2: 2nd portion-   32 a 3: Bent portion-   51: Resin film-   52: Wiring-   60: Insulating sheet

1-4. (canceled)
 5. A solar module comprising: a first solar cell string,a second solar cell string, and a third solar cell string arranged in afirst direction; an extraction electrode of metal foil connectedelectrically to the first solar cell string and drawn to the outside ofthe solar module; and a first wiring member of metal foil electricallyconnecting the second solar cell string and the third solar cell string,wherein each of the first, second and third solar cell stringscomprises: solar cells arranged in a second direction inclined withrespect to the first direction, the solar cells including a terminalsolar cell located at an end of the solar cells in the second direction;a second wiring member bonded to end portions of adjacent solar cells toelectrically connect the adjacent solar cells to each other; and a thirdwiring member having resin film and metal foil arranged on the resinfilm, and electrically connected to an end portion of the terminal solarcell in the second direction, the third wiring member comprises: a firstportion connected electrically to the terminal solar cell with the metalfoil facing the terminal solar cell; a second portion arranged on theterminal solar cell with the metal foil facing away from the terminalsolar cell; and a third portion connecting the first portion and thesecond portion, the terminal solar cell of the first solar cell string,the terminal solar cell of the second solar cell string, and theterminal solar cell of the third solar cell string are arranged in thefirst direction, the first wiring member electrically connects thesecond portion of the third wiring member of the second solar cellstring and the second portion of the third wiring member of the thirdsolar cell string, and when viewed in a normal direction of alight-receiving surface of the solar cells, the extraction electrodedoes not overlap with the first wiring member, the second portion of thethird wiring member of the second solar cell string and the secondportion of the third wiring member of the third solar cell string. 6.The solar module according to claim 5, further comprising an insulatingsheet between the first wiring member and the solar cells.
 7. The solarmodule according to claim 5, wherein a length of the second portion ofthe third wiring member of the first solar cell string in the seconddirection is larger than a length of the second portion of the thirdwiring member of the second solar cell string in the second direction.8. The solar module according to claim 6, wherein the end portion of theterminal solar cell in the second direction is located on an outer sideof the solar module than an end portion of the insulating sheet in thesecond direction.